Why no let or const used ?

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Javascript

I was making a basic alarm in JS and I was following a tutorial and while assigning "now" the programmer dint use any let or const variable and the code is still working fine(the line which is commented out with "Here")...Can someone explain why the code is working without using let or const to initiate the variable?

What I have tried:

<pre>function setAlarm(e) {
    e.preventDefault();
    const alarm = document.getElementById('alarm');
    alarmDate = new Date(alarm.value);
    console.log(`Setting Alarm for ${alarmDate}...`);

 here//   now = new Date();

    let timeToAlarm = alarmDate - now;
    console.log(timeToAlarm);
    if(timeToAlarm>=0){
        setTimeout(() => {
            console.log("Ringing now")
            ringBell();
        }, timeToAlarm);
    }
}